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Chapter 1 25
Signal Generator Overview
Rear Panel
10. I-bar OUT
This female BNC connector (E8267D only) is used with an internal baseband generator
(Option 601/602) to output the complement of the analog, in-phase component of I/Q modulation. On
signal generators without Option 601/602, this female BNC connector is used to output the
complement of the in-phase component of an external I/Q modulation that has been fed into the
Iinput connector.
I-bar OUT is used in conjunction with I OUT to provide a balanced baseband stimulus. Balanced
signals are signals present in two separate conductors that are symmetrical relative to ground and
are opposite in polarity (180 degrees out of phase). The nominal output impedance of the I-bar OUT
connector is 50 ohms, dc-coupled.
11. WIDEBAND Q INPUTS
These female SMA connectors: Q IN (+) and Q-bar IN (−) (Option 016 only) are used with differential
wideband external I/Q inputs. They accept wideband AM and allow direct high–bandwidth analog
inputs to the I/Q modulator in the 3.2−44 GHz range (frequency limit is dependant on the option).
This input is not calibrated. The recommended input power level is −1 dBm with a +/− 1 VDC input
voltage. The nominal impedance for this connector is 50 ohms.
The signal generator uses lowside mixing in the 20–28.5 GHz frequency range (Options 532 and 544),
which reverses the phase relationship for I and Q signals. For internally generated I/Q signals the
signal generator’s firmware compensates for this. However, for wideband external I/Q inputs
(Option 016) there is no compensation and the I and Q inputs at the rear panel must be reversed to
maintain the correct phase relationships in this frequency band. Refer to the Data Sheet and to the
A37 Upconverter description in the Service Guide for more information.
For instruments with Option 015 (discontinued), single-ended wideband I/Q, there is a single BNC Q
input. The recommended power level at this input connector is 0 dBM.
12. COH CARRIER
This female SMA connector (Option UNT only) outputs an RF signal that is phase coherent with the
signal generator carrier. The coherent carrier connector outputs RF that is not modulated with AM,
pulse, or I/Q modulation, but is modulated with FM or ΦM (when FM or ΦM are on).
The output power is nominally 0 dBm. The output frequency range is from 249.99900001 MHz to
3.2 GHz; this output is not useful for output frequencies > 3.2 GHz. If the RF output frequency is
below 249.99900001 MHz, the coherent carrier output signal will have the following frequency:
Frequency of coherent carrier = (1E9 − Frequency of RF output) in Hz.
Damage levels are 20 Vdc and 13 dBm reverse RF power. The nominal output impedance of this
connector is 50 ohms.
13. 1 GHz REF OUT (Serial Prefixes >=US4646/MY4646)
This female SMA connector (Option UNX only) provides a 1 GHz output that is 100 times the
frequency of the internal or external 10 MHz reference. The nominal output level is 7 dBM. The
nominal output impedance is 50 ohms. When not in use, this connector must be terminated with a
50 ohm load.